As a start control apparatus for a cylinder direct injection type internal combustion engine which is subjected to idle stop control, there is known a start control apparatus in which, when fuel feed pressure during an idle stop state goes below a predetermined pressure, fuel is injected to each of a cylinder in which a piston stops in a compression stroke and a cylinder in which a piston stops in an intake stroke and then performs an intake stroke injection at restarting, thereby promptly starting the engine (see, for example, Japanese Patent Application Laid-Open (JP-A) No. 2004-36561). In addition, JP-A Nos. 2001-73774, 2000-213385, and 2202-242724 are other publications with related arts to the present invention.
In case that the internal combustion engine stops due to the idle stop control, the cylinder in which the piston stops in the intake stroke sucks air because an intake valve is opened, and therefore pressure in the cylinder may increase from a negative pressure state at the timing of the stop to atmospheric pressure or therearound. If restarting is performed under such situation, adiabatic compression begins around the atmospheric pressure in the cylinder of the intake stroke, and cylinder temperature exceeds ignition temperature of the fuel, so that self-ignition phenomena may be generated. The self-ignition causes problems such as increasing vibration. The start control apparatus disclosed in JP-A No. 2004-36561 injects the fuel in the cylinder in the intake stroke during the idle stop state merely for the purpose of securing the fuel amount at restarting, and therefore effect of restraining the above-described self-ignition at restarting cannot be expected. Also, the above-described self-ignition problem is not limited to the cylinder direct injection type internal combustion engine but may occur in the so-called port injection type internal combustion engine. Furthermore, the self-ignition problem is not limited to the case of restarting from the idle stop state, but may occur in the case that the internal combustion engine restarts prior to sufficient reduction of the cylinder temperature after the internal combustion engine stops in response to an action of turning the ignition switch off.